1. Field of the Invention
The present invention relates to an exposure time control system and more particularly it pertains to a system for controlling shutter closure in relation with an operation of an electronic flash device upon flash photography.
2. Description of the Prior Art
A camera exposure control system has been proposed which includes a semiconductor switch member for maintaining a shutter control electromagnet at an active condition for arresting a shutter closing member and preventing shutter closure while a main capacitor of an electronic flash device is charged above a given level, said semiconductor switch member allowing shutter closure when the main capacitor is discharged to fire a flash tube, with its charged voltage rapidly dropping. With this system, the shutter is closed immediately after a flash firing.
In this system, however, an ordinary exposure control circuit for controlling the shutter in accordance with light measurement or manual setting is overridden by the semiconductor element and is made ineffective in the flash controlled exposure mode. Accordingly, such system can not apply to an exposure control system wherein an output from an exposure control circuit is utilized for both shutter control and flash duration control.